Catalytically heated fuel processor with replaceable structured supports bearing catalyst for fuel cell

ABSTRACT

A highly compact heat integrated fuel processor, which can be used for the production of hydrogen from a fuel source, suitable to feed a fuel cell, is described. The fuel processor assembly comprises a catalytic reforming zone (29) and a catalytic combustion zone (28), separated by a wall (27). Catalyst able to induce the reforming reactions is placed in the reforming zone and catalyst able to induce the combustion reaction is placed in the combustion zone, both in the form of coating on a suitable structured substrate, in the form of a metal monolith. Fe—Cr—Al—Y steel foils, in corrugated form so as to enhance the available area for reaction, can be used as suitable substrates. The reforming and the combustion zones can be either in rectangular shape, forming a stack with alternating combustion/reforming zones or in cylindrical shape forming annular sections with alternating combustion/reforming zones, in close contact to each other. The close placement of the combustion and reforming catalyst facilitate efficient heat transfer through the wall which separates the reforming and combustion chambers.

FIELD OF THE INVENTION

This invention relates to very compact fuel processor assemblies wherehydrocarbons or oxygenates are reformed to produce a hydrogen richstream which can be fed to a fuel cell for electrical and thermal energyproduction.

BACKGROUND OF THE INVENTION

The use of hydrogen as an alternative energy vector is progressing alongthe road to implementation. The use of hydrogen in fuel cells to produceelectricity or to co-generate heat and electricity, represents the mostenvironmentally friendly energy production process due to the absence ofany pollutant emissions. Most importantly, hydrogen can be produced fromrenewable energy sources, such as biofuels, alleviating concerns overthe long-term availability of fossil fuels and energy supply security.

Large scale production of hydrogen is well understood and widelypracticed in refineries and chemical plants—particularly in the ammoniaproduction industry. For industrial applications requiring smallerquantities, hydrogen is usually transported either cryogenically or inhighly compressed form. The reason is that the technology for largescale hydrogen production cannot be easily downscaled. Furthermore, forhydrogen to be successfully introduced into the transportation anddistributed energy production sectors, refueling and distributionnetworks must be established.

The problem lies in the low energy density of hydrogen which makes itstransportation very inefficient and expensive. Transporting hydrogen incompressed or liquid form requires specialized and bulky equipment. Thisminimizes the amount of hydrogen which can be safely carried, increasingresource consumption and cost. It is, then, apparent that the hydrogeninfrastructure required must be based on distributed productionfacilities. This applies to both, hydrogen as industrial chemical ofmedium or low consumption and, especially, as an energy vector.

Distributed hydrogen production facilities are the focus of numerousresearch and development activities. While the scale of such facilitiesis much smaller than the ones employed in the refineries and the largechemical plants, the basic steps remain the same. The most commonlyemployed method involves hydrogen production by the reformation ofhydrocarbon fuels. These fuels must already have an establisheddistribution network as to address the raw material availabilityconcerns. They include natural gas, propane, butane (LPG) and ethanol asthe representative of the biofuels. Natural gas is mostly methane andcan be reformed according to the reaction:

CH₄+H₂O→CO+3H₂ΔH=49.3 kcal/mol

Propane, butane and ethanol can be reformed according to the reactions:

C₃H₈+3H₂O→3CO+7H₂ΔH=119.0 kcal/mol

C₄H₁₀+4H₂O→4CO+9H₂ΔH=155.3 kcal/mol

C₂H₅OH+H₂O→2CO+4H_(a)ΔH=57.2 kcal/mol

As can be seen from the heats of reaction (ΔH), all of the reformingreactions are highly endothermic, requiring substantial amounts of heatinput which must be covered by an external heat supply. The heat deficitbecomes even larger since the reactions take place at temperatures inthe range of 700-900° C. which means that the reactants must beheated-up to such temperatures.

The reforming reactions typically take place in steam methane reformers.The reforming reaction takes place inside reforming tubes filled with areforming catalyst. The reforming tubes are typically at high pressureof 20-30 bar. The required heat is typically supplied by placing thecatalyst containing tubes of the reactor in rows inside a fired furnace.Between the rows are placed combustion burners that combust fuel and airin an open flame to provide the required heat. The high temperature ofthe flame necessitates that the combustion burners must be placed at asufficient distance from the reforming tubes to prevent the tubes fromhigh temperature exposure which could destroy the tubes. This is arather inefficient arrangement since the hydrogen producing reformingreaction forms a small part of overall reactor. Materials limitationsalso dictate the avoidance of extremely high temperatures (>1000° C.)for the reforming reactor tubes, further limiting the ability to placethe combustion burners in close proximity to the reforming tubes. Allthese mean that traditional steam methane reforming reactorconfigurations are very large and new configurations must be developedto decrease the size and the cost of such systems.

Different configurations have been proposed previously. For reactionsrequiring high heat fluxes, like the reforming reactions, U.S. Pat. No.6,616,909 describe a reactor system consisting of porous foam catalystsin conjunction with microchannel reactors to obtain high rates of heattransfer. Such a configuration presents significant difficulties, suchas excessive pressure drop, which will limit its effectiveness for largescale systems.

U.S. Pat. No. 6,387,554 describes a reactor consisting of a bundle ofsmall diameter ceramic or metallic tubes enclosed in a thermallyinsulated vessel. Catalysts are deposited on the internal and externalsurfaces of the tubes and heat is transferred across the tube walls.

Part of the tubes may not be covered by catalyst and may act as heatexchange zones. Although this system resulted in a compact configurationthe replacement of the catalyst is problematic and, as a result, thewhole reactor must be replaced when the catalyst effectiveness foreither the combustion or the reforming reaction declines.

The reactor described in EP0124226 comprises a double-tube reactorhaving a steam reforming catalyst coated on the outside of the innertube. Alternatively, a set of inner tubes may be mounted in a first tubeplate and a set of outer tubes in a second tube plate, the tube platesbeing disposed across a cylindrical shell so as to define a heatexchange zone. The heat source is a burner. Since the heat source is aburner the limitation of burner placement in relation to the reformingcatalyst placement prevent the construction of a compact low costsystem.

Another reactor described in EP1361919 comprises a tube plate whichcarries a number of elongated pockets extending transversely into ashell. A second tube plate extends across the shell and supports anumber of tubular elongated conduits corresponding to the number ofpockets. The conduits are open-ended and extend into and almost to theend of the pockets. Catalyst may be coated on the surfaces of thepockets and/or the conduits. However, in such a configuration catalystreplacement is problematic.

U.S. Patent Application US2010/0178219A1 by Verykios et al. describes areformer whose tubes are coated with a combustion catalyst on the outersurface and a reforming catalyst on the inner surface. Such aconfiguration results in high rates of heat transport from thecombustion side to the reforming side. However, in such a configurationcatalyst replacement is a problem.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a reformer which produces a hydrogenrich stream by the process known as steam reforming of hydrogencontaining compounds, such as hydrocarbons, oxygenates, etc. Thereformer is comprised of two sections or zones: one where the steamreforming reactions take place and one where combustion of a fuelprovides the heat necessary to carry out the reforming reactions. Thetwo sections are separated by a metal partition and are in close thermalcontact so as to facilitate the efficient transfer of heat from thecombustion to the reforming sections. Combustion takes place over asuitable structured catalyst that can be removed and replaced when itseffectiveness declines. A suitable catalyst support is made of acorrugated metal foil or other structured or ceramic materials,including metal monoliths. Corrugated metal material can be any metal oralloy that can withstand high temperatures, as for example alloys of theformulation FeCrAlY that are typically referred to as fecralloys andhave been widely used as combustion catalyst supports. The combustioncatalyst can be formed by at least one of these corrugated metal foils.Since the catalyst is coated on a separate material, it can be easilyremoved and replaced. The corrugated foil consists of multiple passagesthrough which the combustion mixture can flow but it must also be inclose contact with the combustion tube wall to facilitate efficient heattransfer into the adjacent reforming zone.

Steam reforming is a catalytic reaction and takes place over anothersuitable catalyst. The reforming catalyst can also be coated on acorrugated fecralloy sheet, or similar structure, and placed in thereforming zone, in close contact with the wall separating the reformingand combustion zones.

In one aspect of the invention, a heat integrated combustor/steamreformer assembly is provided for use in a fuel processor. A fuel andsteam mixture is supplied to the reformer to be reformed and a fuel andair mixture is supplied to the combustor to be combusted.

In one aspect of the invention, a heat integrated combustor/steamreformer assembly is provided for use in a fuel processor. A fuel andsteam mixture is supplied to the reformer to be reformed and a fuel andair mixture is supplied to the combustor to be combusted.

As another feature, the integrated combustor/steam reformer assemblyincludes two rectangular sections defined by steel plates in heattransfer relation to each other, as described above. In this case, fueland steam mixture is supplied to one of the rectangular sections whichcontain reforming catalyst coated on corrugated fecralloy sheets whichinduces reforming reactions. A fuel and air mixture is supplied to theother rectangular passage which contains fecralloy sheets coated withsuitable catalyst which promotes combustion reactions. With the use ofsuitably placed baffles (rectangular steel sticks) the fuel and airmixture passage forms an “S” shape. Steel strips placed suitably in theperimeter of the rectangular plate restrict flow to the desireddirection and shape.

In another aspect of the invention the integrated combustor/steamreformer assembly includes a multitude of tubular sections defined byconcentrically placed cylindrical walls separated from each other andsupported on plates machined as to allow some of the cylindrical wallsto pass through them and to be in fluid connection with only one side ofthe plate. One flow passage which passes through the machined plate issurrounded by another one which is restricted by the machined plate. Thelatter is surrounded by a flow passage which passes through the machinedplate and so on. The flow passages which are restricted by the machinedplates communicate through radially placed tubes which form cylindricalchannels through the passages, which pass through the machined plates.The inside wall of the tubular sections are in contact with fecralloysheets, preferably corrugated, coated with a catalyst that induces thedesired reaction. The assembly also includes an appropriately shapedreactor head that facilitates the introduction and distribution of thefuel and air mixture inside the tubular sections and an appropriatelyshaped reactor head that facilitates the collection and exit of thecombustion products. The fuel and steam mixture are introduced to thereformer through a radially placed tube in the outer passage whichcommunicates with the restricted by the machined plates passages throughthe radially placed channels. A second tube, also radially placed, andin flow contact with the opposite axial side of the outer passage,collects the hydrogen rich stream.

According to another feature of the invention, multiple steel plates arebundled together forming rectangular passages. On top of a plate with an“S” shape flow passage containing a catalyst as described above isplaced a straight passage, then a an “S” shape passage flow is placed,and so on. The assembly also includes an appropriately shaped reactorhead that facilitates the introduction and distribution of the fuel andair mixture inside the rectangular passages of “S” shape and anappropriately shaped reactor head that facilitates the collection andexit of the combustion products. An appropriately shaped reactor headfacilitates the introduction and distribution of the fuel and steammixture inside the straight rectangular passages and an appropriatelyshaped reactor head facilitates the collection and exit of the reformingproducts. One of the plates is extended longitudinally in order toseparate the reactor heads of the reforming side in two parts. From thereactor head part which is below the extended plate the fuel and steammixture is inserted in the reactor while from the reactor head partwhich is above the reactor the produced hydrogen is collected.

These and other features and advantages of the present invention willbecome apparent from the following description of the invention and theassociated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of the combustion zone of one embodimentof the invention of the heat integrated reformer with catalyticcombustion, which is of the plate type.

FIG. 1B is a perspective view of the reforming zone of one embodiment ofthe invention of the heat integrated reformer with catalytic combustion,which is of the plate type.

FIG. 1C is a perspective view of another embodiment of the invention ofthe heat integrated reformer with catalytic combustion, which is of thecylindrical type.

FIG. 1D is another perspective view of one embodiment of the inventionof the heat integrated reforming reformer with catalytic combustion,which is of the cylindrical type

FIG. 2A is a perspective view of one embodiment of the invention of theheat integrated reforming reactor with catalytic combustion, comprisingof multiple concentric cylindrical sections.

FIG. 2B is a perspective view of another embodiment of the invention ofthe heat integrated reforming reactor with catalytic combustion,comprising of multiple concentric cylindrical sections.

FIG. 2C is a perspective view of another embodiment of the invention ofthe heat integrated reforming reactor with catalytic combustion,comprising of a stack of multiple rectangular plates.

DETAILED DESCRIPTION

Although the present disclosure will be described in terms of specificembodiments, it will be readily apparent to those skilled in this artthat various modifications, rearrangements, and substitutions may bemade without departing from the spirit of the present disclosure.

The present invention is described in detail with reference to a fewpreferred embodiments illustrated in the accompanying drawings. Thedescription presents numerous specific details included to provide athorough understanding of the present invention. It will be apparent,however, to one skilled in the art that the present invention can bepracticed without some or all of these specific details. On the otherhand, well known process steps, procedures and structures are notdescribed in detail as to not unnecessarily obscure the presentinvention.

FIG. 1A illustrates the “S” shape flow passage of the combustion zone ofa plate-type reformer according to one embodiment of the presentinvention. The combustion flow passage assembly includes a plate 10 thatseparates the combustion zone 11 from the reforming zone. The steelstrips 12 placed suitably in the perimeter of the rectangular platerestrict flow to the desired direction and act as the reactor wall. Afuel and air mixture 13 is supplied through flow passage 14. The flowpassage contains a structured combustion catalyst. An example of astructured catalyst is a fecralloy sheet, preferably corrugated, whichis coated with a combustion catalyst 15 that induces the desiredreaction in the combustor feed. The suitably positioned baffles 16 drivethe combustion flow to form an “S” shape. The flue gases 17 exit thetubular section through flow passage 18. The combustion catalyst couldbe Pt or Pd and combinations thereof or base metals and base metaloxides.

FIG. 1B illustrates the reforming flow passage according to the sameembodiment of the present invention. The flow passage assembly includesa plate 10 (of FIG. 1A) that separates the combustion zone 11 (of FIG.1A) from the reforming zone 20. The steel strips 21 placed suitably inparallel with the rectangular plate, restrict flow to the desireddirection and act as the reactor wall. A fuel and steam mixture 22 issupplied through flow passage 23. The flow passage contains a structuredreforming catalyst. An example of a structured catalyst is a fecralloysheet, preferably corrugated, which is coated with a reforming catalyst24 that induces the desired reaction in the combustor feed. Suitablereforming catalysts include but are not limited to nickel, ruthenium,precious metals and combinations thereof. The reforming products 25 exitthe tubular section through flow passage 26.

The fuel to the combustor can be any available and suitable fuel. Suchfuels include methane, natural gas, propane, butane, liquefied petroleumgas, biogas, methanol, ethanol, higher alcohols, ethers, gasoline,diesel etc. For the embodiment illustrated in FIGS. 1A and 1B, the fuelsnormally available in liquid form must be vaporized before entering thecombustion zone. The same fuels can be fed to the reforming zone toundergo the hydrogen producing reforming reactions. Another potentialfuel to the combustor is the hydrogen depleted off-gas from the anode ofa fuel cell when the reformer is used as a part of a fuel processorproducing hydrogen for a fuel cell, or the hydrogen depleted gas fromhydrogen separation membrane or the hydrogen depleted gas from aPressure Swing Adsorption (PSA) unit.

The composition of the gas mixture entering the combustor should be suchas to ensure complete combustion of the fuel. Although a stoichiometricratio of air to fuel is sufficient, higher ratios can be employed withthe present invention. The composition of the mixture entering thereforming section of the assembly is determined by the stoichiometriesof the reforming reactions for the given fuel. It is typical practice toprovide a higher than stoichiometric steam-to-fuel ratio to minimizepossible side reactions that can cause shoot or carbon formation to thedetriment of the catalyst and/or the reactor. All suitablesteam-to-carbon ratios in the range from 1 to 25 can be employed withthe present invention.

The structured combustion catalyst can preferably be in the form of acorrugated metal foil made of a high temperature resistant metal ormetal alloy. A metal alloy such as an alloy with the formula FeCrAIY,commonly referred as fecralloy, can be used for high temperaturecombustion catalyst support. The wall 10 can be constructed from anymaterial, but materials that offer low resistance to heat transfer suchas metals and metallic alloys are preferred. In this configuration, heatis generated by combustion in the catalytic chamber and is transportedvery easily and efficiently though the wall 10 to the reforming chamberwhere the heat demanding reforming reactions take place. Heat isgenerated where it is needed and does not have to overcome significantheat transfer resistances to reach the demand location resulting in highefficiencies. The presence of a catalyst and lower temperatures permitsignificantly higher space velocities to be used compared to flame basedreformers. Space velocity is defined as the ratio of the feed flow atstandard conditions to the empty volume of the reactor. For the catalystsection of the heat integrated reformer space velocities of 1000 to100000 hr⁻¹, more preferably 5000-50000 hr⁻¹ and even more preferably10000 to 30000 hr⁻¹ can be used. In flame based reformers spacevelocities are typically bellow 2000 hr⁻¹.

The catalyst on the reforming side can be a structured catalyst, inwhich case high space velocities can be used, preferably 10,000-100,000hr⁻¹ or, more preferably, 7,500-15,000 hr⁻¹.

The suitable combustion and the reforming catalysts can be prepared bycoating a relatively thin (5-1000 μm thick) catalytic film on thefecralloy sheets. Suitable catalysts typically consist of a support andone or multiple metal phases dispersed on the support. The support istypically a metal oxide that may contain oxides of one or multipleelements from the IA, IIA, IIIA, IIIB and IVB groups of the periodictable of elements. The most typical combustion catalysts support isaluminum oxide. The dispersed metal phase may contain one or multipleelements from the IB, IIB, VIB, VIIB and VIII groups of the periodictable of elements. One method to prepare the catalytic film that ensuresgood adhesion to the fecralloy is to heat the fecralloy sheet toelevated temperatures in air. During the heating, aluminum, which is acomponent of the fecralloy, is diffusing out of the bulk of the alloyand forms an aluminum oxide surface layer. Upon this surface layer it iseasy to coat alumina or other metal oxide supports for the desireddispersed metal phase which may be a precious or non-precious metal.Typical supports for reforming and combustion catalysts consist ofoxides of aluminum, silicon, lanthanum, cerium, zirconium, calcium,potassium and sodium. The metal phase of reforming catalysts may containnickel, cobalt, copper, platinum, rhodium and ruthenium. The metal phaseof the combustion catalyst may contain platinum, palladium, rhodiumnickel or any other metal that is active in catalytic combustion.

Coating of the catalysts support on the fecralloy sheets can beaccomplished by many techniques. After heating up so as to form thealuminum oxide layer at the surface, techniques such as dip coating froma solution of dispersed metal oxide particles or from a slurry whichcontains the metal oxide particles can be employed. Alternatively,catalyst can be deposited on the fecralloy sheets by spraying thecatalytic components onto their surface, or by plasma deposition, etc.The catalyst support is then dried by calcination at elevatedtemperatures. The dispersed metal phase can be added to the supportforming solution or slurry of the metal oxide particles or it can beadded in a separate step from a solution of the desirable metal saltafter the calcination step.

The temperatures and pressures of the two streams entering thecombustion zone and the reforming zone, respectively, need not to be thesame. Typically, combustion takes place at low or near-atmosphericpressure, although high pressure combustion is practiced. Reforming cantake place at pressures somewhat above atmospheric up to 30 barg. Thewall of the flow passages should be of sufficient strength to allow forthe pressure differential between the two streams.

The major advantage of the present invention is the heat integrationbetween the combustion 11 and the reforming 20 zones. Combustion takesplace on the catalytic film which is coated on the structured catalyst15 placed on one side of the plate 10 separating the two zones. The heatthat is generated on the combustion side is quickly transferred and usedon the reforming side. This rapid heat transfer is critical inmaintaining the combustion side catalyst at temperatures below 1200 Cand more preferably below 1000 C. These temperatures ensure acceptablecatalyst life and permit the use of a very compact combustion zone whichallows the reactor assembly to be dramatically smaller compared with aflame based reformer which needs to maintain a significant distancebetween the flame generation and the reforming sections. The lowertemperatures also allow the use of less expensive alloys for theconstruction of the reactor. The lower temperatures also mean that thereare no nitrogen oxide emissions as their formation require much highertemperatures.

FIG. 1C illustrates a lateral cross-section of an integrated reformeraccording to another embodiment of the present invention. The integratedcombustor/steam reformer assembly includes a tubular section defined bya cylindrical wall 27 which separates the combustion zone 28 from thereforming zone 29. The assembly housing 30 acts as the reactor wall anddefine an axially extending concentric annular passage in heat transferrelation with the tubular section. In the center of the combustion zonea tapped tube 31 is inserted so as to reduce the combustion flow crosssection area.

FIG. 1D illustrates an axial cross section of the same integratedreformer as illustrated in FIG. 1C. The integrated combustor/steamreformer assembly includes a tubular section defined by a cylindricalwall 27 that separates the combustion zone 28 from the reforming zone29. The assembly housing 30 acts as the reactor wall and defines anaxially extending concentric annular passage in heat transfer relationwith the tubular section. In the center of the combustion zone a tappedtube 31 is inserted so as to reduce the combustion flow cross sectionarea.

A fuel and air mixture 32 is supplied to the tubular section throughflow passage 33. In this embodiment the flow passage of the tubularsection contains the combustion catalyst 34 deposited on a corrugatedfecralloy sheet that induces the desired reaction in the combustor feed.Similarly, the outside of the tubular section contains fecralloy sheetscoated with reforming catalyst 35 that induces the desired reaction inthe reformer feed. The products of the combustion reactions 36 exit thetubular section through flow passage 37. A fuel and steam mixture 38 issupplied to the annular passage through flow passage 39 counter-currentor co-current to the combustion gases. The products of the reformingreactions 40 exit the annular passage through flow passage 41.

The reactor assembly includes a flow distributor 16 as to allow foruniform feeding of the annular combustion zone 28. The flow distributorconsists of a cylindrical cross section 42 and multiple perforatedsheets 43 placed against the combustion feed flow passage. Theperforated steel sheet 43 has holes of 0.5-1 mm diameter with a densityof 20-50 holes per cm2 and subsequently a flow area which is 5-20% ofthe flow area of the cylindrical cross section 42. Due to the pressuredrop created on the perforated sheet, the flow of the gas is distributedevenly in the cylindrical cross section 42. In a way, the holes of theperforated sheet act as spraying nozzles and the flow distributor as astatic mixer with a pressure drop of 15-250 mbar, which is much lowerthan the commonly used static mixers. The size and the density of theperforated sheet holes as well as the distance between the perforatedsheets is of critical importance and depends on various reformer sizingparameters such as capacity, type of fuel, desired pressure drop etc.The preferable distance between perforated sheets is 15-50 mm.

FIG. 2A and FIG. 2B illustrate one embodiment of a complete heatintegrated reforming reactor, which is of the cylindrical form. Thereactor consist of multiple cylindrical cross sections 44 placedconcentrically forming combustion flow passages 45 in contact withreforming flow passages 46. Reforming flow passages communicate throughradially placed cylindrical channels 47. A fuel and air mixture 48 issupplied to the annular sections through flow passage 45. The combustionflow passages 45 contain the combustion catalyst 50 deposited on acorrugated fecralloy sheet that induces the desired reaction in thecombustion zone. Similarly, the reforming flow passages 46 containfecralloy sheets coated with reforming catalyst 51 that induces thedesired reaction in the reforming zone. The products of the combustionreactions 52 exit the reactor through flow passage 49. A fuel and steammixture 53 is supplied to the annular passages through flow passage 46and cylindrical channels 47 counter-current or co-current to thecombustion gases. The products of the reforming reactions 54 exit theannular passage through radial channels 47 and flow passage 46.

This embodiment may contain also a flow distributor for uniform feedingof the combustion flow passage as described in FIG. 1D.

FIG. 2C illustrates another embodiment of a complete heat integratedreforming reactor with catalytic combustion, which is of the plate form.The reactor consists of multiple rectangular steel sheets 55 placed oneon top of the other forming combustion flow passages 56 in contact withreforming flow passages 57. Reforming flow is restricted in reformingflow passage with steel rectangular strips 58 placed accordingly.Combustion flow is restricted in combustion flow passage with steelrectangular strips 59 placed accordingly. Combustion flow may have an“S” type flow shape as briefly described in FIG. 1A. A fuel and airmixture 60 is supplied to the combustion passage 56. The combustion flowpassages 56 contain the combustion catalyst 62 deposited on a corrugatedfecralloy sheet that induces the desired reaction in the combustor feed.Similarly, the reforming flow passages 57 contain fecralloy sheetscoated with reforming catalyst 63 that induces the desired reaction inthe reformer feed. The products of the combustion reaction 64 exit thereactor through rectangular combustion flow passages 56. A fuel andsteam mixture 65 is supplied to the reforming catalyst 63 throughreforming flow passages 57 and cross flow to the combustion gases. Theproducts of the reforming reactions 66 exit the reactor throughreforming passage 57.

The heat integrated reforming reactor configurations described aboveoffer several advantages over the conventional flame-based reformingreactors. The catalytic combustion takes place at lower temperatures,which permits close coupling of the combustion and reforming zones. In aflame based reformer, the flame must be at a significant distance fromthe tube containing the reforming catalyst to prevent the tube frommelting. As a result, the integrated reforming reactor is several timessmaller than a flame-based reforming reactor and, consequently, has amuch lower capital and installation cost. The flame-based reformers canconsist of hundreds of tubes and burners and a sophisticated feed flowdistribution system is required to distribute the combustion feed andreforming feed to all burners and tubes evenly. The heat integratedreformer has a single inlet for the reforming and single inlet for thecombustion feed gases which results in simple and inexpensive feed flowsystem. The flame reformers, even with the use of low NOx burners, stillproduce significant quantities of NOx in the combustion gases, whichhave to be controlled with a separate selective catalytic reduction(SCR) catalyst and ammonia injection. The heat integrated reformerdescribed within operates at low temperatures on the combustion side atwhich NOx formation is negligible.

The fuel feed to the reformer can be natural gas, liquefied petroleumgas (LPG), propane, naphtha, diesel, ethanol or other biofuels, orcombinations of these fuels.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations and equivalents thatfall within the scope of the present invention and have been omitted forbrevity. It is therefore intended that the scope of the presentinvention should be determined with reference to appended claims.

1-8. (canceled)
 9. An integrated steam reformer/combustor assembly foruse in a fuel processing system that supplies a steam and fuel mixtureto the reforming zone to be reformed and produce hydrogen and a fuel andair mixture to the combustion zone to be combusted and provide the heatto the reformer, the assembly comprising: a multitude of tubularconcentric sections where the internal wall of the tube is contactedwith a catalyst dispersed in the form of a thin film on fecralloysheets, said catalyst being able to induce the combustion reactions; theexternal wall of the tube is contacted with a catalyst, in the form of athin film coated on fecralloy sheets, said catalyst being able to inducethe reforming reactions; a cylindrical wall enclosing the tubularsections and bonded to the tube sheets and having flow passages forfeeding the reforming reactants and removing the reforming products; afirst reactor head connected to one tube sheet and having a flow passagefor feeding the combustion feed; and a second reactor head connected tothe other tube sheet and having a flow passage for removing thecombustion products.
 10. The assembly of claim 9 further comprising aflow distributor inside the first reactor head and connected to itsassociated flow passage. 11-15. (canceled)
 16. An integrated steamreformer/combustor assembly according to claim 9 further including aflow distributor inside the first reactor head for distributing thecombustion feed.